Namaz - Objections and Counterobjections

You asked:
Do classical Arabic dictionaries give the metaphorical meaning of words and sentences composed of words?

AFAIK yes they do. Many idioms are recorded in classical arabic dictionaries. There is a work on verbal idioms of Quran by mustansir mir, available to download free as pdf, but it does not contain all idioms, but many.

As I said, with regards to the ablution verses I have personally never seen anyone able to make an alternative explanation fit. The only way it can fit is to say these idioms do not exist elsewhere and in terms of cross-reference 4:43/5:6 are unique occurrences in Quran. In terms of evidence, this is rather poor.